This disclosure relates generally to novel terminal structures for wiring devices for use in electrical apparatus and in systems incorporating such electrical apparatus. A possible, but by no means exclusive, application for the use of the example terminal structures for wiring devices is within electrical receptacle assemblies having push-in wire termination. Such electrical apparatus may be configured, for instance, as a duplex plug outlet, a grounding duplex plug outlet, a light switch or light bulb socket for commercial or residential use, which will be more generally referred to simply as receptacle assemblies. A plurality of such example receptacles may be electrically connected together to form a wiring system such as for use in an enclosure, such as a room, where the receptacles may be installed in walls, floors and/or ceilings.
Historically, with respect to terminal structures for wire termination in wiring devices, in receptacles, such as duplex plug outlets, there have been many terminal structures that include a clamping fastener, such as a screw. However, these structures require bending of a conductive stripped end of a wire, so as to encircle the shaft of the screw, and additional time and labor in backing the screw outward to accommodate the wire and then tightening the screw to affect a proper connection.
Other duplex plug outlets have used push-in wire termination structures of one of three basic types. The first type includes a push-in contact that is integrally formed as spring fingers that extend from the major brass structure that also is configured to engage a plug contact. These types of structures have encountered problems due to the stress-relaxation inherent in such brass structures, which lead to failure of the wire connection. They also are less effective when used with stranded wires which may spread out width wise during insertion and over time.
The second type of push-in wire termination structure includes a push-in contact that is formed by having a spring finger held by a housing in a position opposite a major brass structure that is configured to engage a plug contact and is held in a separate position within housing. These types of structures add complexity by having to properly place and hold multiple separate components within a housing during and after completing assembly of the housing. Also an inserted wire tends to push apart the spring finger and the major brass structure in these types of terminal structures, which then must be resisted by the portions of the housing that are configured to hold the separate components. In addition, these types of structures do not offer the opportunity to provide any productive conductivity by the separately held spring finger and do not tend to have structures that will force stranded wires together to retain a consistent level of compression.
The third type of push-in wire termination structure includes a contact assembly that requires the wire to be pushed into the receptacle and then further manipulated, such as by sliding the wire into a slot that has a pair of opposed flanges that are designed to cut through the wire insulation and engage the conductor within the wire. These types of structures add complexity that is necessary to allow the user to accurately manipulate the wire after insertion, while still leaving some uncertainty as to the extent of the engagement because of the need to penetrate the wire insulation while also not cutting through the conductive end of the wire.
Thus, prior art terminal structures for wiring devices may be found in numerous forms and suffer from a variety of disadvantages that may potentially result in reduced effectiveness over time, reduced conductivity, increased complexity of assembly, and/or increased time and labor required during installation.